I think Duplicity (http://duplicity.nongnu.org) is what you're looking for. For Ubuntu I know there's a nice GUI that anyone who can use a computer can set up. For other platforms I think cli is the only way, but someone could just write a QT/Cocoa wrapper around it.
Design a simple system that uses amazon as backend to store encrypted data and the keys never leave your control.
There were 4TB drives at 100-sh bucks for big things.
The problem is not Cryptolocker because there will ALWAYS be malware that targets the data itself. And some people will do it just for fun.